Fix issue with StompSubProtocolHandler initialization

This change ensures that StompSubProtocolHandler is injected with an
ApplicationEventPublisher for both the Java and XML config.

Backport for:
0dddb6f3e1
4372dac002

Issue: SPR-11825

spring-websocket/src/test/java/org/springframework/web/socket/config/MessageBrokerBeanDefinitionParserTests.java

@@ -118,6 +118,8 @@ public class MessageBrokerBeanDefinitionParserTests {
 		assertNotNull(stompHandler);
 		assertEquals(128 * 1024, stompHandler.getMessageSizeLimit());
 
+		assertNotNull(new DirectFieldAccessor(stompHandler).getPropertyValue("eventPublisher"));
+
 		httpRequestHandler = (HttpRequestHandler) suhm.getUrlMap().get("/test/**");
 		assertNotNull(httpRequestHandler);
 		assertThat(httpRequestHandler, Matchers.instanceOf(SockJsHttpRequestHandler.class));